A fifth person has been arrested in connection with the terrorist attack in Manchester on Monday night, police said this afternoon.

Four people have been arrested today, after Prime Minister Theresa May revealed the terror threat has risen to "critical", suggesting another attack on UK soil remains highly likely and could be imminent.

Armed military personnel have been deployed on British streets in response to the threat.

The level, decided by terrorism experts from across the security services, has not been critical since nearly a decade ago. It was upgraded from "severe".

"This means that their assessment is not only that an attack remains highly likely but that a further attack may be imminent," the PM said.

On Monday night 22 people were killed by a terrorist at a concert in Manchester. Greater Manchester chief constable Ian Hopkins revealed the identity of the suicide bomber as 22-year-old Salman Abedi. Islamic State has claimed responsibility for the atrocity.

"Work undertaken throughout the day has revealed that it is a possibility we cannot ignore that there is a wider group of individuals linked to this attack," the PM said. May said Abedi was "born and brought up in Britain".

Soldiers may be deployed to concerts and sporting events in the coming days, May also warned. "Armed police officers responsible for duties such as guarding key sites will be replaced by members of the armed forces, which will allow the police to significantly increase the number of armed officers on patrol in key locations," she said.